Paul wrote, "You will know (by my letters) how people ought to conduct themselves in God’s household, which is the church of the living God, the pillar and foundation of the truth." 1Tim 3:15The "church" is not a building nor an institution. The church is the collective assembly of the believers. While the institutional forms associated with the assembling of Christians together are neither individually nor collectively "the Church", institutional churches have been established to facilitate the ministry among the family of God - much like as in one's own family. You grew up in a house which you called home. But it really isn't the building itself but the family relationships with constitute the home. So also in the church. The believers don't "go" to church, they "are" collectively the church.
While the entire of the Christian community is the family of God of which Christians are commanded to love, yet in meeting the needs of the Christian community there are many aspects which can only practically be carried out in smaller groups. Even Jesus, while he carried on a public ministry, also limited part of his ministry to smaller groups, such as his twelve apostles. Institutional churches are one place where small groups of believers meet for the purpose of edification as outlined in Ephesians 4:11-16. If that's where Christians have chosen to meet, then one may be remiss in their duty to love other Christians if they choose not to get involved there. However keep in mind also that there are inherent effects of institutionalism which also hinder the ministry which must be overcome if one is to grow and minister effectively or comprehensively in such an environment. So in a sort of "Matthew 23 fashion" let me mention some pitfalls of institutional christianity to avoid.
I appeal to you, brothers, in the name of our Lord Jesus Christ, that all of you agree with one another so that there may be no divisions among you and that you may be perfectly united in mind and thought. My brothers, some from Chloe’s household have informed me that there are quarrels among you. What I mean is this: One of you says, "I follow Paul"; another, "I follow Apollos"; another, "I follow Cephas"; still another, "I follow Christ." Is Christ divided? Was Paul crucified for you? Were you baptized into the name of Paul? 1Cor 1:10-13Denominationalism is inherently divisive, demanding unity around the opinions of institutional leadership, and the object of such unity tends to be forms and programs as well the interpretations of the institutional elite. But Christian unity unites around Christ - as defined in the Bible. Institutionalism tends to develop an "our church vs your church" mentality in the Christian community. But the Bible teaches that we are to view all believers as belonging to one family.
In responding to questions of faith, people with institutionalized faith tend to respond like, "you'll have to ask my pastor what I believe about that", or refer to the opinions of their denominational post-Biblical theologian, whereas Biblical faith is one in which first of all one understands what one believes, and one is personally convinced of it, the content being what the Bible actually says.
And here is a significant point to guard against the effects of institutionalism - personal Bible study. Dare to develop your own convictions based upon what you are convinced is the meaning and application of the Bible. Challenge others and allow others to challenge you concerning such convictions and applications. Another significant point is to keep in mind that your objective is to love the brethren by meeting their needs, while also allowing them to minister to you for your edification.
Other downsides of institutionalism is that they tend to emphasize programs over people, forms over function, rituals over relationships, and tend to devalue individuals, rather measuring "fruitfulness" purely be increasing numbers - regardless of whether such numbers are dominated by weeds. Afterall Paul warned that a little leaven leavens the whole lump. And thus what is popular is seldom that which is pure.
The blame for such corruption is due to our inherent sinful nature. These kinds of effects are found both in religious and secular institutions. It is not purely the institutional leaders to be blamed. Though their positions tend to have a rather predictable effect upon their attitudes. Generally speaking the pride of position which comes also from the need to justify one's salary tends to create a condescending clergy-layman attitude within institutional leaders, reckoning "their congregation" a bunch of stupid sheep. You'll find them taking great pauses in their speech, as if their congregation is just too mentally slow to keep up with their line of reasoning. And if you have a Bible study run by an institutional leader it'll tend to be a lecture format and end up being an indoctrination session rather than a serious study of the Bible. And rather than challenging discussion oriented questions, if they allow questions at all, the questions will tend to be leading questions or so simple as not to invite any discussion. In fact discussion and fellowship tend to be discouraged due to the effect of institutionalism. For most Christians, they go to church service, sit down, say only what the program tells them to say, pay their dues, listen to a sermon, and go home. If that's all instutional Christianity has to offer, it should be reckoned only a minor part of the Christian life. But lazy Christians may find it convenient to limit or define their Christian life thusly. They attend the weekly program and reckon themselves as having fulfilled their spiritual responsibility - if indeed they even think in terms of responsibility. Such Christians reckon themselves nothing but stupid sheep incapable of doing nothing but the most simplest of tasks, and thus excused themselves from doing any serious Christian work. Like lifelong infants they look only for places where their "needs" can be met, or only what they can get out of it, reckoning ministry to be only the job of institutional leadership or paid professionals.